I've used Finale for years. They have several cheaper versions now that seem to do everything us guitar guys would need but I haven't checked them out. SInce I'm transitioning the studio to Mac I need to actually buy a new notation program for my office (running Finale 2006 in a Windows XP simulator is getting old) so I'm actually looks at what is out there right now.
Shouldn't you be able to get a crossgrade for a Mac version? Email them and they can probably help you out.
The last version I paid for was 2002
Checked out finale notebook today and really couldn't get the swing of it.
FWIW, I downloaded the latest (free/opensource) tuxguitar and found it quite good! Check it out if you get a chance. I really like the guitar chord editor.